Field of the Invention
Embodiments of the present invention relate generally to a shot data generation method and a multi charged particle beam writing method, and more specifically, relate to a method for generating shot data in multi-beam writing, for example.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a pattern on a wafer and the like with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multiple beams (multi beams) can be cited. Compared with the case of writing a pattern by using a single electron beam, since it is possible to emit multiple beams at a time in multi-beam writing, the throughput can be greatly increased. For example, in a writing apparatus employing a multi-beam system, multiple beams are formed by letting an electron beam emitted from an electron gun assembly pass through a mask with a plurality of holes, blanking control is performed for each of the beams, and each unblocked beam is reduced by an optical system and deflected by a deflector so as to irradiate a desired position on a target object or “sample” (refer to, e.g., Japanese Published Unexamined Patent Application (JP-A) No. 2006-261342).
In multi-beam writing, since the number of beams is large, the amount of data for controlling an irradiation time period is enormous. For example, in the case where the number of beams is n×m and each irradiation time period data is k bits (for example, ten bits), the data amount of one irradiation is n×m×k bits. Then, it is necessary to transmit the data from the control unit to the irradiation unit within an irradiation time period. If the irradiation time period is, for example, around Tμs, the transmission speed of n×m×k/(T×10−6) bps is needed. For example, the transmission speed of hundreds of Gbps is needed. For example, even when using a product with a transmission speed of 100 Gbps, several parallel lines are needed. If using a product with a transmission speed of 20 to 40 Gbps from a viewpoint of reliability of the current product, several tens or more of parallel lines are needed, which may cause a problem of difficulty in physical configuration. Therefore, it is necessary to reduce the data amount and to improve the writing method.